The present invention relates to a system for purifying water containing immiscible organic compounds and, more particularly, relates to a system for removing toxic impurities and immiscible organic compounds, such as terpenes, from water after it has been used as a rinse or wash in a cleaning device.
In the production of circuit boards and other parts, it is necessary to wash thoroughly the completed circuit board or component with a cleaning solution which is capable of removing all traces of fluxes, solder pastes, and other contaminants remaining from the manufacturing process. Some cleaners employ volatile CFC's such as freon as the cleaning solvent. Although these solvents offer the advantage of not requiring a rinse or wash subsequent to cleaning because they evaporate from the surface of the circuit board, they are harmful to the atmosphere and have thus been banned in many locations. The disadvantages associated with these solvents have led to a search for more acceptable solvents.
Some of the problems associated with CFC solvents can be avoided through the use of organic solvents which are less volatile and are not harmful to the atmosphere. However, since these less volatile materials have a low evaporation rate, the product must be rinsed with water and then dried to remove the solvent from the product. Water rinsing removes the remaining solvent and rinses away the remaining residues.
While this process effectively cleans the circuit boards or parts, it produces large volumes of waste water which are contaminated with the organic solvent and the toxic substances removed by the solvent. This problem is alleviated somewhat by the fact that many of the organic solvents suitable for such purposes are substantially immiscible with water, i.e., only minimally soluble in water. These solvents thus typically form a two-phase system with water and can be removed to a large extent through physical separation. However, since these compounds are not completely immiscible and thus cannot be completely separated from water, a system employing a separation device still produces large amounts of contaminated waste water which generally contains too high a level of organic and/or toxic impurities to permit discharge into septic systems or some sewer systems without further treatment.
To avoid these problems, systems have been proposed which purify the waste water and recycle it to the cleaner. One such system includes a decanter or separation tank which separates the major part of the solvent from the water, thus partially purifying the water, and filtration and treatment devices which are designed to complete the purification process and to recycle the water back to the cleaner.